Project 2 will focus on two primary goals. The first concerns the electrophysiological changes that occur with age and their relationship to neuroanatomic changes in the brain (MRI) and neuropsychologic test scores. Toward this end, data from 200 optimally healthy subjects (approximately 100 ales and 100 females) will be examined. Most of these data will have been gathered in previous funding periods, however, some data will be gathered in the next funding period in order to permit state-of-the-art MRI analyses. A variety of statistical techniques will be employed to evaluate age-related change, including principal components, EEG coherence, and EP covariance analyses of the quantified neurophysiologic data (QEEG). The second primary goal of Project 2 concerns dementia of the Alzheimer type (AD). One hundred and twenty five questionable cases of AD (CDR=0.5) and forty normal controls (CDR=0) will be followed for a minimum of 3 years. It is anticipated that approximately 2/3 of the questionable cases (n=800 will be categorized as AD by the end of the follow-up period. This will permit an examination of the electrophysiological differences between questionable cases who are diagnosed as AD on follow-up and questionable cases who are not. It will also permit the evaluation of the relationship between QEEG data, cognitive test scores and other quantified neuroimaging measures (i.e., MRI, SPECT) in these very mildly impaired patients.